Heat oil in a pan
Add mustard seeds and let them splutter
Add cumin seeds, curry leaves, and dried red chilies
Add chopped onions and sauté until soft
Add chopped tomatoes
Add salt, turmeric, and red chili powder
Cook until the tomatoes turn soft and mushy
Add tamarind pulp or a little vinegar if desired
Add jaggery or sugar to balance the taste
Cook until the chutney thickens
Turn off the heat
Let it cool slightly
Serve with idli, dosa, rice, or snacks